Operative Planning

• Diagnostic angiography should be performed with specific views that provide excellent visualization of all feeding vessels, nidus, and the venous drainage pattern.
  
• Rapid frame rates and superselective angiography are frequently required to better delineate the angioarchitecture and hemodynamics of the AVM.
  
• Rotational angiography may be helpful for small, deep AVMs, particularly those in the posterior fossa and to evaluate associated aneurysms.
  
• If endovascular cure is not possible, the strategy for embolizing AVMs is to obliterate as many of the feeding vessels as possible to make surgical resection easier and safer. The utility of embolization prior to gamma knife therapy is somewhat controversial.

Special Equipment

• A 6 to 6.5 French (F) sheath
  
• A 6F guiding catheter
  
• Flow-directed or over-the-wire microcatheters
  
• 0.035-inch guide wire and micro–guide wires
  
• A 5F catheter (for diagnostic angiogram)
  
• N-butyl-2-cyanoacrylate (NBCA)
  
• Ethiodized oil
  
• Tantalum powder
  
• Five percent dextrose
  
• Onyx liquid embolic system (ev3 Neurovascular, Irvine, CA)

• Monitored anesthetic care can be used to allow provocative testing prior to embolization of a feeding vessel.
  
• Some neurointerventionalists perform all AVM embolizations under general anesthesia and do not perform provocative testing, particularly when using the Onxy liquid embolic system, which typically requires prolonged infusion times.
  
• Occasionally, 30 to 90 seconds of hypotension (systolic blood pressure ~80) is induced at the time of NBCA embolization to allow for maximum control of the glue injection.
  
• Protamine should be readily available if intraoperative rupture occurs.

Monitoring

• Provocative testing is performed with the use of amobarbital and cardiac lidocaine injections of the feeding vessels through the microcatheter to determine that embolization will not result in a neurologic deficit.
  
• Somatosensory evoked potentials and motor evoked potentials may be used in the embolization of spinal AVMs.

Positioning

• The patient is placed in the supine position.
  
• Intravenous antibiotics, if needed, are given.
  
• A Foley catheter is placed.
  
• The proper shielding is placed on the patient.
  
• Both inguinal areas are shaved and prepped with iodine solution.
  
• A sterile drape is placed over the prepped areas.
  
• The head is positioned in neutral position and gently taped in place.

Technique

Sheath Removal

• The sheath is removed and a closure device is often used for the femoral artery puncture site.
  
• Many endovascular therapists reverse the heparin with protamine.